On 04/07/2014 02:18 AM, Thierry Reding wrote: > On Fri, Apr 04, 2014 at 04:31:05PM -0600, Stephen Warren wrote: >> From: Stephen Warren <swarren@xxxxxxxxxx> >> >> BIT_WORD() truncates rather than rounds, so the loops in >> syncpt_thresh_isr() and _host1x_intr_disable_all_syncpt_intrs() use <= >> rather than < in an attempt to process the correct number of registers >> when rounding of the conversion of count of bits to count of words is >> necessary. However, when rounding isn't necessary because the value is >> already a multiple of the divisor (as is the case for all values of >> nb_pts the code actually sees), this causes one too many registers to >> be processed. >> >> Solve this by using and explicit DIV_ROUND_UP() call, rather than >> BIT_WORD(), and comparing with < rather than <=. >> >> Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> >> --- >> v2: Use DIV_ROUND_UP rather than BITS_TO_LONGS to avoid problems on 64-bit. >> --- >> drivers/gpu/host1x/hw/intr_hw.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) > > If I understand correctly there's no immediate need for this to go to > stable kernels, nor for it to be queued for 3.15, right? That is the > potential extra write isn't causing any harm on actual hardware, is it? > > In that case I'll queue this up for 3.16. We should definitely apply this, and as far back as the code exists, since the SW is touching non-existent registers, and that is presumably undefined behaviour, which could potentially cause hard-to-diagnose bugs. Besides, I want the mainline kernel to run on our simulator without having to maintain patches for fixed issues. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
