On 21/11/2014 13:41, Hannes Reinecke wrote:
> Using DMA for command submission has the drawback that it might
> generate additional DMA completion interrupts after the command
> has been submitted to the device.
> Additionally the am53c974 has a design flaw causing it
> to generate spurious interrupts even though DMA completion
> interrupts are not enabled.
> This can be avoided by using the FIFO for command submission.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/scsi/esp_scsi.c | 46 +++++++++++++++++++++++++++++-----------------
> drivers/scsi/esp_scsi.h | 1 +
> 2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
> index 0ad0f08..2a3277d 100644
> --- a/drivers/scsi/esp_scsi.c
> +++ b/drivers/scsi/esp_scsi.c
> @@ -143,6 +143,24 @@ void scsi_esp_cmd(struct esp *esp, u8 val)
> }
> EXPORT_SYMBOL(scsi_esp_cmd);
>
> +static void esp_send_dma_cmd(struct esp *esp, int len, int max_len, int cmd)
> +{
> + if (esp->flags & ESP_FLAG_USE_FIFO) {
> + int i;
> +
> + scsi_esp_cmd(esp, ESP_CMD_FLUSH);
> + for (i = 0; i < len; i++)
> + esp_write8(esp->command_block[i], ESP_FDATA);
> + scsi_esp_cmd(esp, cmd);
> + } else {
> + if (esp->rev == FASHME)
> + scsi_esp_cmd(esp, ESP_CMD_FLUSH);
> + cmd |= ESP_CMD_DMA;
> + esp->ops->send_dma_cmd(esp, esp->command_block_dma,
> + len, max_len, 0, cmd);
> + }
> +}
> +
> static void esp_event(struct esp *esp, u8 val)
> {
> struct esp_event_ent *p;
> @@ -650,10 +668,7 @@ static void esp_autosense(struct esp *esp, struct esp_cmd_entry *ent)
>
> val = (p - esp->command_block);
>
> - if (esp->rev == FASHME)
> - scsi_esp_cmd(esp, ESP_CMD_FLUSH);
> - esp->ops->send_dma_cmd(esp, esp->command_block_dma,
> - val, 16, 0, ESP_CMD_DMA | ESP_CMD_SELA);
> + esp_send_dma_cmd(esp, val, 16, ESP_CMD_SELA);
> }
>
> static struct esp_cmd_entry *find_and_prep_issuable_command(struct esp *esp)
> @@ -789,12 +804,12 @@ build_identify:
> }
>
> if (!(esp->flags & ESP_FLAG_DOING_SLOWCMD)) {
> - start_cmd = ESP_CMD_DMA | ESP_CMD_SELA;
> + start_cmd = ESP_CMD_SELA;
> if (ent->tag[0]) {
> *p++ = ent->tag[0];
> *p++ = ent->tag[1];
>
> - start_cmd = ESP_CMD_DMA | ESP_CMD_SA3;
> + start_cmd = ESP_CMD_SA3;
> }
>
> for (i = 0; i < cmd->cmd_len; i++)
> @@ -814,7 +829,7 @@ build_identify:
> esp->msg_out_len += 2;
> }
>
> - start_cmd = ESP_CMD_DMA | ESP_CMD_SELAS;
> + start_cmd = ESP_CMD_SELAS;
> esp->select_state = ESP_SELECT_MSGOUT;
> }
> val = tgt;
> @@ -834,10 +849,7 @@ build_identify:
> printk("]\n");
> }
>
> - if (esp->rev == FASHME)
> - scsi_esp_cmd(esp, ESP_CMD_FLUSH);
> - esp->ops->send_dma_cmd(esp, esp->command_block_dma,
> - val, 16, 0, start_cmd);
> + esp_send_dma_cmd(esp, val, 16, start_cmd);
> }
>
> static struct esp_cmd_entry *esp_get_ent(struct esp *esp)
> @@ -1646,7 +1658,7 @@ static int esp_msgin_process(struct esp *esp)
>
> static int esp_process_event(struct esp *esp)
> {
> - int write;
> + int write, i;
>
> again:
> write = 0;
> @@ -1872,6 +1884,10 @@ again:
> if (esp->msg_out_len == 1) {
> esp_write8(esp->msg_out[0], ESP_FDATA);
> scsi_esp_cmd(esp, ESP_CMD_TI);
> + } else if (esp->flags & ESP_FLAG_USE_FIFO) {
> + for (i = 0; i < esp->msg_out_len; i++)
> + esp_write8(esp->msg_out[i], ESP_FDATA);
> + scsi_esp_cmd(esp, ESP_CMD_TI);
> } else {
> /* Use DMA. */
> memcpy(esp->command_block,
> @@ -1949,11 +1965,7 @@ again:
> case ESP_EVENT_CMD_START:
> memcpy(esp->command_block, esp->cmd_bytes_ptr,
> esp->cmd_bytes_left);
> - if (esp->rev == FASHME)
> - scsi_esp_cmd(esp, ESP_CMD_FLUSH);
> - esp->ops->send_dma_cmd(esp, esp->command_block_dma,
> - esp->cmd_bytes_left, 16, 0,
> - ESP_CMD_DMA | ESP_CMD_TI);
> + esp_send_dma_cmd(esp, esp->cmd_bytes_left, 16, ESP_CMD_TI);
> esp_event(esp, ESP_EVENT_CMD_DONE);
> esp->flags |= ESP_FLAG_QUICKIRQ_CHECK;
> break;
> diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h
> index 975d293..27dcaf8 100644
> --- a/drivers/scsi/esp_scsi.h
> +++ b/drivers/scsi/esp_scsi.h
> @@ -478,6 +478,7 @@ struct esp {
> #define ESP_FLAG_WIDE_CAPABLE 0x00000008
> #define ESP_FLAG_QUICKIRQ_CHECK 0x00000010
> #define ESP_FLAG_DISABLE_SYNC 0x00000020
> +#define ESP_FLAG_USE_FIFO 0x00000040
>
> u8 select_state;
> #define ESP_SELECT_NONE 0x00 /* Not selecting */
>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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