On 14-11-04 08:57 PM, Stephen Warren wrote:
On 10/30/2014 12:36 AM, Scott Branden wrote:
The bcm2835 has clock domain issues when back to back writes to certain
registers are written. The existing driver works around this issue with
udelay. A more efficient method is to store the 8 and 16 bit writes
to the registers affected and then write them as 32 bits at the appropriate
time.
diff --git a/drivers/mmc/host/sdhci-bcm2835.c b/drivers/mmc/host/sdhci-bcm2835.c
static void bcm2835_sdhci_writew(struct sdhci_host *host, u16 val, int reg)
{
struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
- struct bcm2835_sdhci *bcm2835_host = pltfm_host->priv;
- u32 oldval = (reg == SDHCI_COMMAND) ? bcm2835_host->shadow :
- bcm2835_sdhci_readl(host, reg & ~3);
+ struct bcm2835_sdhci_host *bcm2835_host = pltfm_host->priv;
Is that type change for bcm2835_host really correct?
Yes - at the top of the patch the structure has been expanded and named
appropriately.
-struct bcm2835_sdhci {
- u32 shadow;
+struct bcm2835_sdhci_host {
+ u32 shadow_cmd;
+ u32 shadow_blk;
};
+ } else {
+ /* Read reg, all other registers are not shadowed */
+ oldval = readl(host->ioaddr + (reg & ~3));
Is there any reason to use readl() directly here rather than calling
bcm2835_readl()? ...
Yes, bcm2835_readl does not need to be called in read-modify-write and
shadow register situations and just adds overhead. All that needs to be
called is readl. bcm2835_readl has some existing ugly code in it to
modify the capabilities register on a read function. This info never
needs to be for write as you can't overwrite the capabilities register.
I hope to get rid of the capabilities hack in a future patch as this
should never have been acceptable in upstreamed code to begin with. The
capabilities override should have been passed in through a device tree
entry.
static void bcm2835_sdhci_writeb(struct sdhci_host *host, u8 val, int reg)
{
- u32 oldval = bcm2835_sdhci_readl(host, reg & ~3);
+ u32 oldval = readl(host->ioaddr + (reg & ~3));
... and here in particular, since this seems like an unrelated change?
Same situation with bcm2835_readl above. No need to call in
read-modify-write situations.
static int bcm2835_sdhci_probe(struct platform_device *pdev)
{
struct sdhci_host *host;
- struct bcm2835_sdhci *bcm2835_host;
+ struct bcm2835_sdhci_host *bcm2835_host;
Is that type change for bcm2835_host really correct?
yes - structure renamed above
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